Minecraft doesn't have any significant modding support from the developer. Official 'mods' are mostly limited to textures / shaders. The real modding tools that exist for Minecraft were created by the community and largely exist because Java is comparatively easy to reverse engineer in addition to some 'off the record' style support of the mod lib authors by the game developers. The whole mod scene has gone through various phases of questionable legality and unknown future. The Minecraft mod scene exists largely in spite of the game developer, not due to it.
Official mod support (with an installer and an API) was on the dev roadmap but never materialized.
I think the distribution networks and art assets still make it more effective than unity for testing game concepts. And that's what leads to games like Battle Royale and DOTA.
It's also safer. Running executables (with full access to your user account) from random people on the internet is the quickest way to get pwned. Games with built-in mod support often sandbox any code within the mod so that it doesn't have unrestricted access to your machine. (Any game with automatic mod downloading upon server join better be doing this at least.) So it's both easier and safer to try out games (er, mods/maps) on random people's suggestions. (Same goes for browser-based games, since browsers sandbox all code in web pages.)
starting with most accessible:
Modders<->Unity Devs<->Unreal Devs<->Custom C++ engine devs
Yet for every AAA development house that can't prioritize making public versions of their in house development tools, there are games like Minecraft that are almost nothing but modding tools pretending to be games, and getting all sorts of interesting fans doing interesting things.
Where most AAA game engines used to make modding easy but licensing to sell mods hard, there are now entire engines (Unity, Unreal) with fairly simple, linear (as opposed to exponential or worse) license systems that allow hobbyists to build with the same tools of AAA developers and license their work for resale, growing organically with their audience size rather than being constrained to artificial limits of steep license curves.
It's one of those cases where it's both better than its ever been and worse than it ever was, and you can write clickbait articles for both sides of that, but overall, unclouded by nostalgia glasses the answer is probably just that it's the same as it ever was.